25-Hydroxy Vitamin D3 Molecule Structure:

Chemical name: (3b,5Z, 7E)-9,10-Secocholestra-5,7,10(19)-triene-3,25-diol
Due to the unsaturated double bonds at the 5,7,10 positions, it is very easy to be oxidized and degraded, so the market always need a stable formulation to minimize the degradation loss.
Current product on the market is a micro-encapsulation form (U.S. Pat. No. 8,088,410): first, the 25-Hydroxy Vitamin D3 is dissolved in the vegetable oil, add some anti-oxidant into the oil phase, this is the oil phase. The modified starch is added into the water to make the aqueous phase. Then add the oil phase into aqueous phase while mixing, then this mixture is homogenized to form an emulsion, the 25-Hydroxy Vitamin D3 containing oil was dispersed as tiny oil droplets, with diameter less than 5 um, this emulsion was spray dried to form a fine powder.
There are two problems with current product form, first, since the 25-Hydroxy is dissolved in the oil at molecule level, the starch layer could not stop the oxygen diffusion into the oil phase, it can be oxidized in the air. Its shelf-life is about six month under cold storage condition. When this product exposed to accelerated stability test at 45° C., there is more than 20% loss of active after one week. This add lot of cost to the product for overage and the short shelf-life also add a lot problems for transportation and storage of the product.
The other problem is with its low bioavailability due to the active being dissolved in oil phase, it is not water soluble, it will be absorbed by the small intestine in an animal very slowly, so it cannot be absorbed very well due to the short residence time in the small intestine.